Blast nozzle for self-blasting compressed gas electric circuit-breakers

ABSTRACT

An axial blast breaking chamber for self-blasting compressed gas electric circuit breakers wherein the chamber wall is provided with a plurality of radial holes having an entrance to the inside of said breaker chamber through a ring-like feeding groove coaxial to the longitudinal axis of the chamber. When the contacts are closed the fixed contact, which is in close proximity to the inner wall of the chamber, extends past the feeding groove thereby inhibiting flow of quenching gas. Flow of quenching gas remains inhibited until the chamber and attached movable contact are displaced sufficiently to withdraw the feeding groove and radial holes below the lower end of the fixed contact.

United States Patent Calvino y Teijeiro [54] BLAST NOZZLE FOR SELF-BLASTING COMPRESSED GAS ELECTRIC [2]] App]. No.: 134,269

[30] Foreign Application Priority Data April 16, 1970 Italy ..23394 A/70[52] US. Cl.... ..200/l48 R, 200/148 A [51] Int. Cl. ..H0lh 33/70 [58]Field of Search ..200/l48 A, 148 G, 148 C, 148 R [451 June 13, 1972Primary Examiner-Robert S. Macon AttorneyStevens, Davis, Miller & Mosher[57] ABSTRACT An axial blast breaking chamber for self-blastingcompressed gas electric circuit breakers wherein the chamber wall isprovided with a plurality of radial holes having an entrance to theinside of said breaker chamber through a ring-like feeding groovecoaxial to the longitudinal axis of the chamber. When the contacts areclosed the fixed contact, which is in close proximity to the inner wallof the chamber, extends past the feeding groove thereby inhibiting flowof quenching gas. Flow of quenching gas remains inhibited until thechamber and attached movable contact are displaced sufficiently towithdraw the feeding groove and radial holes below the lower end of thefixed contact.

6 Claims, 4 Drawing Figures PATENTEnJum m2 Y 3.670.125

SHEET 1 OF 2 INVENTOR.

BENITO JOSE CALVINO Y TEIJEIRO WOQ WW TORNEYS PATENTEDJUM 1s zen BENITOJOSE CALVINO Y sum 2 0F 2 22 vrvL INVENTOR TEIJEIRO OR EY The object ofthis invention is to provide an improved blast nozzle for self-blastingcompressed gas electric circuitbreakers, which provides substantialimprovement in the performance of the breaking chambers employed in saidcircuitbreakers in comparison with known types. Compressed gascircuit-breakers are already well known and widely used in electricgenerating and distributing systems and well known are, in particular,the axial blast breaking chambers, used in these types ofcircuit-breakers, the shape of which has, in its various embodiments,been determined through widely known principles.

In relatively recent times the applicant has filed some other patentapplications (against one of them Italian Pat. No. 791,651 has beengranted, while others are still pending, one of them under reference24973-A/69) concerning axial blast breaking chambers for self-blastingcompressed gas electric circuit-breakers having a nozzle shape providedwith decompression holes and ring-like grooves, said holes and groovesbeing formed to favor the escape of both the gases developed by thedecomposition of the materials making up the breaking chambersthemselves and the quenching gas, thus obtaining a concomitant flow ofthe first and latter mentioned gases, said breaking chambers havingtheir downstream (or end) parts dependently relating to thecircuit-breaker rated service voltage according to the experimentalrelation (simplified form:

L 2 v1.5 U,,),

wherein L stands for the chamber end part length, stated in,

mm, and U, is the circuit-breaker rated service voltage expressed in kV.

It has been found, however, that the known axial blast breaking chambersdo not exhibit optimum performance with respect to the arc quenching gasexhaust.

An object of this invention is, therefore, to provide a breaking chamberfor compressed gas electric circuit-breakers which is structurallyimproved incomparison with the known chambers, and particularly inconnection with the breaking chambers of similar type previouslydisclosed by the applicant.

A further object of this invention is to provide improvements in thebreaking chambers of electric circuit-breakers whereby the holes madethrough the chamber walls particularly favor the decompression in thenonle zone having the smallest cross section, where said holes havetheir entrance thereby permitting the quenching gas to escape withparticular ease.

A still further object of this invention is to provide an axial blastbreaking chamber wherein it is still possible to reach, and indeed toimprove, the combination of the efiects of the quick decompression inthe entrance zone of the through-wall holes as well as of the bestpossible course concomitance of the decomposition gases and thequenching gas flows through the end (or downstream) part of theinterruption chamber itself, consequently accelerating the outflow ofthe whole of said gases through the outlet orifice of the chamber anddecreasing the whirl effects occurring in the total outflow.

These and other objects, which those skilled in the art can betterdeduce from the following detailed description, are profitably reachedby an axial blast breaking chamber for selfblasting compressed electriccircuit-breakers, said breaking chamber having a blast nozzle internallyshaped in way to provide, in the outlet direction, a first conical andconvergent zone, a second cylindrical zone having the smallestcross-sectional area in comparison with the other internal zones and athird substantially conical and divergent zone, the length of which isdetermined from the already known experimental relation said thirdconical and divergent zone having a plurality of ringlike grooves eachof which is substantially triangular sectioned within a plane passingthrough the chamber axis with open base towards the outlet orifice ofthe breaking chamber, said breaking chamber having a plurality oflateral outlet means, through the chamber wall corresponding to saidsecond smallest cross-sectioned cylindrical zone, which communicateamong themselves in the chamber inside, where said outlet means havetheir own entrance sections, through a ring-like feeding groove coaxialto the breaking chamber itself.

The breaking chamber which is the object of this invention will behereinafter more detailedly described with reference to the encloseddrawings, wherein FIG. 1 schematically shows the longitudinal section,of the breaking chamber according to this invention, marked by brokenline A-A'on FIG. 2, i.e., along two different axial planes.

FIG. 2 schematically shows a plan view of the same breaking chambercross-sectioned in correspondence with plane BB on FIG. 1.

FIG. 3 illustrates the breaking chamber of FIGS. 1 and 2 with thebreaker contacts in their closed position, and

FIG. 4 illustrates the breaking chamber with the contacts in the openposition.

Referring to these figures, the improvement in the nozzle of thebreaking chamber for self-blasting compressed gas electriccircuit-breakers, being the scope of this invention, consists inproviding a chamber with the following features: substantial nozzleshape according to the Venturi tube principle, with a second (or neckedand smallest surfaced) zone 5 cylindrically shaped and provided with aplurality of decompression holes 6 for allowing the communication ofsaid cylindrical smallest surfaced zone 5 with the breaking chamberouter room, said holes 6, unlike the similar decompression holes of theknown art, having rather reduced diameters and being in numberconsiderably greater than the number of holes used in known breakingchambers. The number of holes ranges from six, as a minimum, to amaximum solely limited by its compatibility with the restrictionsimposed by the technological manufacturing requirements, namely themechanical machining work the chamber has to undergo for obtaining saidholes. Since large diametered holes can be made in smaller number andvice versa, and since the axes of said holes are radial to the chamberand lie within a common cross section plane of the same chamber, it isclear that an interference exists between the diameter and number ofholes. The concerned improvements consists moreover in providing aring-like (consequently coaxial to the breaking chamber and particularlyto cylindrical zone 5) groove 22, made in the inner wall of the abovespecified smallest surfaced cylindrical zone 5, having the task of ringor duct feeding all decompression holes 6, said ring-like groove 22having a substantially rectangular radial cross section with height hcorrelatively depending on the diameter d of holes 6 and depth 1suitably dimensioned according to the breaking chamber serviceconditions. Entrance sections 10 of holes 6, which open to the inside ofthe breaking chamber (or, more exactly, to the bottom of ring-likegroove 22), are parallel to breaking chamber axis YY in consequence ofthe shape of said groove 22. Holes 6 pass through the wall of saidchamber and their sections for the debouchment into open air arereferenced 1 1 on the figures.

Referring to FIGS. 3 and 4, the fixed contact 30 and movable contact 31are shown positioned within the nozzle, movable contact 31 being securedto and moving with said nozzle. When the circuit-breaker is closed, thefixed contact 30 occupies a large portion of the space within thebreaking chamber;

i.e., the whole truncated cone divergent zone 9 of the chamber fixedcontact 30, being in close proximity to the inner wall surface ofcylindrical zone 5, even if not fully tight, substantially hampers thequenching gas outflow, except the neglectable quantities which canescape through the usual mechanical clearances due to the machiningtolerances.

As the opening operation continues, as shown in FIG. 4, the fixedcontact 30 no longer blocks ring-like groove 22 and holes 6. Thequenching gas outflow is from this moment established through saidring-like groove 22 and holes 6. The exhaust section area corresponds,at this moment, to the sum of the areas of the openings offered by holes6.

In consequence of the breaking chamber parting from fixed contact 30, assoon asthe fixed contact lower end reaches the beginning of zone 9, alsothe sections of this zone, (said sections being substantially circularcrown shaped in that they are determined inside by the above specifiedfixed contact and outside by the inner wall of said zone 9) areavailable for the outflow both of the quenching gas and thedecomposition gases. The example illustrated by the figures illustrates12 holes 6 symmetrically arranged and, therefore,

reciprocally displaced by 30. It should be noted, however,

that as already mentioned, said holes can be at least six and may bemore than, 12 compatible with the manufacture requirements. (However,too small a number of decompression holes should be avoided since thisreduces the number of the, outflow paths which in accordance with theinvention should be as large as possible, compatibly with the conditionthat each hole has s sufficiently dimensioned opening).

.Remarkable results can be attained in this way: first, regularizationin the gas flow through radial decompression holes 6, thanks to whichthe outlet from said holes becomes much easier, consequently granting aquicker decompression of cylindrical zone and reduction of the whirleffects, inside the concerned zone and generally the whole breakingchamber," to a neglectable value.

Each hole 6 made through the wall of cylindrical zone 5 is, I

in fact, a point attracting the quenching gas to the outlet way and themore of these points there are, the better are the even- ,nessconditions of the plasma which sets up the electric arc in consequenceof the better quenching gas distribution. To this aim, however, theavailability of ring-like groove 22 appears as detenninant, clearlycharacterizing the nozzle concemed by the present invention in respectto the known art. Groove 22 acts, in fact, as a chamber for equalizingthe quenching gas pressure thereby improving its distribution amongthe'various holes and making uniform, as already said, the eddyconditions whereto the electric plasma is submitted. Through thissolution, infact, the electric arc is surrounded by a full quenching gassleeve and nearly attacked by an electric action, deionizing andquenching, which while always advantageous, is even more beneficial atthe initial are striking stage when the fixed contact is still withincylindrical zone 5, consequently still keeping the nozzle closed, buthaving freed groove 22 and, in consequence, also holes 6. The quenchinggas can in this way very energetically influence the whole of the juststriken electric are by a blast and eddy action which, instead of beingconcentrated in the points whereat the arc is facing the holes, isdistributed on its whole circumference.

The advantages obtained with this invention are increased by theadvantages due to the particular shape of the chamber end zone 9provided with ring-like triangularly cross-sectioned grooves 1 3, due towhich the resultants of the elementary flow lines of the decompositiongases offer a component, parallel to axis Y-Y, which favors the outflowof both the quenching (or deionizing) gas and the decomposition gases.Although this detail of the chamber has been already described in aprevious applicants patent, it is seen that, in the same chamber, theaddition of the effects reached through the present and the foregoinginvention permits the attainment, with regard to a quicker and fullerarc. quenching, of .more effective results than could be attained byhaving separate and single recourse to the above pointed out solutions.

The present invention has precisely the advantage of not in the leastaltering zone 9 of the chamber, the constructional shape of which hasbeen experienced and led to remarkable success, and of only slightlyaltering zone 5 of the chamber, thus obtaining the advantages of thepeculiar features of both zones. Ring-like groove 22, and also holes 6,can in fact be differently dimensioned but its availability does notparticularly alter the nozzle construction. As already mentioned, saidringlike groove has, preferably, a radial rectangular cross sectionwhich can however be also triangular, semicircular, or otherwisesuitably shaped.

Evidently modifications and alternatives can be brought to theinvention, as hereinabove described, exemplified, illustrated, andhereunder claimed, without getting out of the inhave their axis notperpendicularly positioned toward chamber axis Y-Y but suitablyslanting, towards axis Y-Y, in that direction which provides animprovement in the gas outflow, precisely to define towards said axisY--Y an angle smaller than in the direction of the chamber outletorifice Moreover, ring-like groove 22, which together with the relevantplurality of holes 6 characterizes this invention, provides improvementsin the operation of the circuit-breakers, when used in similarly styledbreaking chambers of the known art.

What is claimed is: 1. In an axialblast breaking chamber forself-blasting compressed gas electric circuit breakers having fixed andmovable contacts (30, 31), a blast nozzle internally shaped to provide,in the outlet direction, a first conical and convergent zone (1 a secondcylindrical zone (5) and a third substantially conical and divergentzone (9) having a length L equal to or greater than i I where U,, is therated service voltage of said circuit breaker,

said second zone (5) having a cross-sectional area not greater than thatof said first and second zones, and said third zone (9) having aplurality of ring like grooves (13) each of which has a substantiallytriangular cross section within a plane passing through the longitudinalaxis (Y--Y)'of the chamber, said ring-like grooves being open toward theoutlet orifice (2) of the breaking chamber, wherein the improvementcomprises having a plurality of lateral outlet means (6), through thechamber wall corresponding to said second smallest cross-sectionedcylindrical zone (5), which outlet means (6) communicate amongthemselves in the chamber inside, where they have their own entrancesections (10), through a ring-like feeding groove (22) coaxial to thelongitudinal axis (Y-Y) of the breaking chamber itself.

2. An axial blast breaking chamber as defined by claim 1 wherein saidchamber is provided with at least six lateral outlet means.

3. An axial blast breaking chamber as defined by claim 1 wherein saidlateral output means are radial holes having circular cross sections.

4. An axial blast breaking chamber as defined by claim 1 wherein saidlateral outlet means areradial holes having a 7 diameter (d) as small aspossible, compatibly with gas outflow requirements, and thereby providethe maximum number of holes in said chamber wall.

5. An axial blast breaking chamber as defined by'claim 3 wherein saidring-like feeding groove (22) is, with respect to a plane passingthrough the chamber axis, substantially rectangular in cross section andhas a height (h) at least equal to the diameter (d) of the radial outletholes.

hibiting flow of the quenching gas, said flow continuing to be inhibiteduntil said movable contact and nozzle are displaced sufficiently towithdraw said ring-like feeding groove (22) below the lower end of saidfixed contact.

I k '0 I

1. In an axial blast breaking chamber for self-blasting compressed gaselectric circuit breakers having fixed and movable contacts (30, 31), ablast nozzle internally shaped to provide, in the outlet direction, afirst conical and convergent zone (1), a second cylindrical zone (5) anda third substantially conical and divergent zone (9) having a length Lequal to or greater than where Un is the rated service voltage of saidcircuit breaker, said second zone (5) having a cross-sectional area notgreater than that of said first and second zones, and said third zone(9) having a plurality of ring-like grooves (13) each of which has asubstantially triangular cross section within a plane passing throughthe longitudinal axis (Y-Y) of the chamber, said ringlike grooves beingopen toward the outlet orifice (2) of the breaking chamber, wherein theimprovement comprises having a plurality of lateral outlet means (6),through the chamber wall corresponding to said second smallestcross-sectioned cylindrical zone (5), which outlet means (6) communicateamong themselves in the chamber inside, where they have their ownentrance sections (10), through a ring-like feeding groove (22) coaxialto the longitudinal axis (Y-Y) of the breaking chamber itself.
 2. Anaxial blast breaking chamber as defined by claim 1 wherein said chamberis provided with at least six lateral outlet means.
 3. An axial blastbreaking chamber as defined by claim 1 wherein said lateral output meansare radial holes having circular cross sections.
 4. An axial blastbreaking chamber as defined by claim 1 wherein said lateral outlet meansare radial holes having a diameter (d) as small as possible, compatiblywith gas outflow requirements, and thereby provide the maximum number ofholes in said chamber wall.
 5. An axial blast breaking chamber asdefined by claim 3 wherein said ring-like feeding groove (22) is, withrespect to a plane passing through the chamber axis, substantiallyrectangular in cross section and has a height (h) at least equal to thediameter (d) of the radial outlet holes.
 6. An axial blast breakingchamber as defined by claim 1 wherein said movable contact (31) issecured to said nozzle and, when said circuit breaker is closed, thefixed contact (30) extends into said first conical and convergent zone(1), the outer surface of said fixed contact being in close proximity tothe inner wall surface of said cylindrical zone (5) thereby inhibitingflow of the quenching gas, said flow continuing to be inhibited untilsaid movable contact and nozzle are displaced sufficiently to withdrawsaid ring-like feeding groove (22) below the lower end of said fixedcontact.